The present invention involves cellulose material and superabsorbent polymers. Cellulose material and the art of manufacture of cellulose material are well known to those skilled in the art. For example, cellulose material and the process to manufacture are discussed in the book entitled “Handbook for Pulp and Paper Technologist” (Angus Wilde Publications Inc., 1992) by Gary A. Smook.
General background of the manufacture of superabsorbent polymers can be seen in the journal article, “Keeping Dry with Superabsorbent Polymers”, Chemtech, (September, 1994) by Buchholz. This article contains an excellent discussion of the conventional methods for making superabsorbent polymers. Also mentioned are various uses of superabsorbent polymers such as in disposable diapers, in a sealing composite between concrete blocks that make up the wall of underwater tunnels, and in tapes for water blocking in fiber optic cables and power transmission cables.
More general background with respect to various superabsorbent polymers and their methods of manufacture can be seen in U.S. Pat. No. 5,229,466 (issued Jul. 20, 1993) to Brehm and Mertens; U.S. Pat. No. 5,408,019 (issued Apr. 18, 1995) to Mertens, Dahmen and Brehm; and U.S. Pat. No. 5,610,220 (issued Mar. 11, 1997) to Klimmek and Brehm, all of which patents are assigned to Chemische Fabrik Stockhausen GmbH.
Superabsorbent polymers have been used to coat absorbent fibers and drying the coated fibers as disclosed for example see U.S. Pat. No. 4,962,172 (Issued Oct. 9, 1990) to Allen et al; and U.S. Pat. No. 5,160,789 (issued Nov. 3, 1992) to Barcus et al. Cellulose fibers have a retention capacity or CRC of about less then 2 g/g i.e. cellulose fibers are considered to be a non-absorbent fiber. Furthermore, coating fibers with a polymer solution generally adversely affects the fibers other properties such as wicking power and makes the fiber brittle.
Another approach of adhering SAP to fibers is by the graft polymerization techniques as disclosed in U.S. Pat. No. 4,986,882 (issued Jan. 22, 1991) to MacKey et at. This approach discloses processes for making highly absorbent tissues and towels by wet-laying pulps comprising particular polycarboxylate polymer-modified fibrous pulps such as mildly hydrolyzed methyl acrylate-graft softwood kraft pulps. Graft polymerization method is a complicated method that requires a multi-step purifying process to remove the homopolymer and unreacted monomers.
Forming an absorbed layer of polyelectolyte on cellulose fibers is disclosed in the article Studies on Interfacial Properties of Polyelectrolyte-Cellulose Systems, J. Applied Polymer Science, Volume 22, pages 3495-3510 (1978).
The disclosures of all the above-mentioned patents and published patent applications are incorporated by reference.